Autism rates in the United States rose by 30% between 2008 and 2010, and by 120% between 2000 and 2010, according to a new study by the Centers for Disease Control and Prevention. One in 68 8-year-old children had been diagnosed with autism by 2010, up from 1 in 88 two years earlier, says the report. These are staggering statistics, compared to the 1 in thousands ratio of American children who had been diagnosed as autistic in 1970.

The study, published online in late March, 2014, found that five times as many boys as girls are being diagnosed with autism. The CDC estimates that 1 in 42 boys has autism, and 1 in 189 girls. Caucasian children are diagnosed most frequently, followed by Hispanics, then African-Americans. The average age at which children are diagnosed has fallen, but remains above age 4 (diagnosis is possible by age 2).

Many experts believe that a portion of the increase in autistic cases can be attributed to better awareness and diagnosis of the illness, though that would seem to only account for a smaller fraction of the manifold increase in autism diagnoses in recent years.

One known factor that ups risk of autism is the aging of modern parents — in the case of autism, the aging of fathers; studies have shown that autism risk in children increases with paternal age at conception.

Whereas the risk of chromosomal mutations such as Down syndrome becomes greater with increasing maternal age, in the case of some complex mental disorders, including autism (and schizophrenia), paternal age has been found to be a much greater risk than maternal age (Nature online, August 22, 2012). Even when the mother is in her early 20’s, a father who is at least 11 years older than the mother is more likely to have a child with mental health difficulties, including autism (Malaysian Mental Health Survey, published online in March, 2011).

Scientists do not know whether the increased autism risk for older fathers is the result of age-related mutations that build up in men’s genes over time, or whether it reflects that men have been exposed for longer to environmental agents that directly damage their genetic material.

For its latest figures, the CDC reviewed medical and school records from 2010 for 8-year-old children at 11 states across the U.S. The states included were: New Jersey (with the highest rate of autistic children, at 1 in 46), Arizona, Arkansas, Colorado, Georgia, Maryland, Missouri, North Carolina, Utah, Wisconsin and Alabama (with the lowest incidence, at 1 in 175 children). A CDC spokesperson said that the great rate variation among states is due at least in part by states’ different resources in identifying and serving children with autism.

To be diagnosed with an autism spectrum disorder, a person must show deficits in three areas: communications, social skills and typical behavior. Almost half of the children in the CDC study had average or above-average intelligence (“average” was defined as having an IQ higher than 85), compared to a third of autistic children a decade ago.

Some doctors believe that the rates of autism in the CDC study are too high: children are now being diagnosed with autism even when they have average or above-average intelligence. Until twenty years ago, children who were diagnosed as autistic always had intellectual disabilities; doctors did not diagnose children as autistic when the youths had average or above-average intelligence. One doctor observed that some present-day diagnoses of autism in high-functioning kids could be simply cases of ADHD (attention deficit / hyperactivity disorder) with social immaturity. Other children might have intellectual challenges, but not have autism per se.

From birth to age 5, children reach milestones in how they communicate and interact with the world around them. Symptoms of autism usually appear before age 3 (and last throughout the child’s life). Autism symptoms can range from mild to severe, and they include:

Difficulty with verbal or non-verbal communication

Difficulty with social interaction or wanting to play alone

Playing with toys and objects in unusual ways

Repetitive body movements

Preoccupation with unusual objects

Experts advise parents who have concerns about their children’s early play, speech or behavior to discuss those concerns with their doctors and caregivers; if your child attends school, ask the school how to get a free evaluation. The earlier an autistic child begins receiving therapy, the more the child’s deficits can be minimized. But it is never too late to get help for your child.